The trio all pleaded not guilty to murder at their 2009 trial but were convicted and sentenced to serve at least 19 years in jail.

Ben's sister, Brooke, played Kelly Taylor in Albert Square from 2001 to 2004. She is presenting a new BBC3 show examining restorative justice, where criminals can get to meet their victims face to face.

'Can Criminals Say Sorry?' airs on April 14 and will highlight the Government's pledge to spend £30million on making restorative justice more widely available.

Brooke - in her role as an ambassador of the independent charity Victim Support - agreed to investigate the process.

But despite seeing many victims benefit from meeting offenders, she admitted she may never be ready to face her brother's killers.

In her letter Brooke, 30, says she is still haunted by every stab wound her brother suffered that night.

She writes: "For almost six years there hasn't been a day when I haven't planned out exactly what I would say to you if I ever had the chance.

"I imagine you will never bother to read this but all I want is for you to hear exactly what you took away that night. If you have one ounce of decency in you, please take five minutes to read this in the hope it can somehow make you understand.

"Obviously you all have mothers and probably brothers and sisters too. One of you even has a son.

"My mum had one son. His name was Ben. And you took him from her. She had to bury her son at the age of 16. She had to open his exam results and see he had achieved mainly A grades and she wasn't even able to give him a kiss to say how proud she was of him.

"For six years I have watched my mum and dad visit a cold stone almost every week and kiss the top of it as if they are kissing their son's head, as that is all they have left of him.

"Please think about your mums now. I don't know how they feel about what you did but I'm sure you still get to see them and kiss and hug them. My mum can never, EVER do that to her child again.

"One of you is a dad. I am sure you love your son and would do anything to keep him from getting hurt. Do you understand how painful it is to see your dad break down because he couldn't keep his son from harm? As a family we often blame ourselves for YOUR actions.

"I was Ben's big sister. I loved him more than life itself. He was my little brother but he acted like my big brother and, if he could, he would have protected me my whole life.

"I couldn't protect him from you and this has made me feel so guilty ever since.

"Because of you I missed out on buying my brother a pint on his 18th birthday. I've missed out on watching him fall in love and giving him advice when he had his heart broken. We sat in that hospital for five hours and prayed for Ben to make it.

"You stabbed him 11 times. We had to hear about every injury, from its length to its width. His longest one was 18cms long. Do you know how much that number haunts me in my sleep?

"I know there is no reason you could ever give me as to why you did this – and the worst thing is I don't believe you had a reason. Your five seconds of horrific, unnecessary violence destroyed so many lives that night – your own included, though you will still come out one day and be able to live again. My family will never be able to do that properly.

"The sound of his laugh is fading from my memories. All we can do is look at photos where he is frozen at 16. I try to picture the man he would have grown up to be and I can't. But I know without a doubt he would have been a good one.

"I don't want apologies or excuses from you. I just wanted to have the chance to say to you the things I scream in my nightmares pretty much every night.

"I'll never be able to fully explain what you took from us when you killed Ben – but I hope this goes some way towards showing you."